In general, a rotary electric machine comprises a stator, a rotor mounted on a shaft and a casing with supports for the rotor shaft.
To mount the stator and the rotor in the casing, the latter must be divided into at least two parts which can be assembled.
An example of an electric machine and a method for making it is known from patent U.S. Pat. No. 5,767,596.
Also known, especially in the sector of electric fans for motor vehicles, are watertight and moisture proof electric motors.
Such motors are designed to operate in environmental situations and in positions in which they may be subject to infiltration by water and moisture, which may create electrical problems for the motor.
There have been prior art attempts to make a watertight casing for electric motors, in particular made by inserting a gasket between the two parts mentioned above, for example as described in document WO2005/034309 by the Applicant.
However, this type of assembly is not without disadvantages: in particular, when the motor is closed, that is to say when the lid and the cup-shaped part are locked relative to one another, there is no absolute guarantee that the motor will be hermetically sealed.
Despite the many efforts made to ensure this, the gasket between the two parts of the casing may not be perfectly positioned or effectively squashed to guarantee a suitable seal between the parts in contact.
Moreover, infiltrations may occur at the motor shaft supports, in particular where the motor shaft comes out of the casing for motor effectiveness.